Chapter 6: Bones and Bone Tissue - Anatomy Study Guide PDF

Objectives- Chapter 6- Bones and the Bone Tissue 1. Describe the functions of the skeletal system. - Skeletal system functions A. Protection- protects vital organs B. Mineral storage and acid-base homeostasis; stores minerals; calcium and phosphate C. Blood cell fo...

Objectives- Chapter 6- Bones and the Bone Tissue 1. Describe the functions of the skeletal system. - Skeletal system functions A. Protection- protects vital organs B. Mineral storage and acid-base homeostasis; stores minerals; calcium and phosphate C. Blood cell formation- red bone marrow is the site of blood cell formation D. Fat storage- yellow bone marrow stores triglycerides E. Movement- muscles produce movement via their attachment to bones F. Support- supports the weight of the body 2. Describe how bones are classified. Provide examples of each shape. a. Long- named for shape; Longer than they are wide o Ex- arms and legs b. Short- named for shape; roughly cube-shaped or about as long as they are wide o Ex- bones of wrists (carpals) and ankles (tarsals) c. Flat- thin and broad bones o Ex- ribs, pelvis, sternum (breastbone), and most bones in the skull d. Irregular- includes vertebrae and certain skull bones o Do not fit into other classes because of irregular shapes e. Sesamoid- specialized bones located within tendons; usually small, flat, and oval-shaped; give tendon a mechanical advantage o Patella (kneecap) 3. Describe the gross structure of long, short, flat, irregular, and sesamoid bones. Define diploe Long bones: - Periosteum- forms a covering, blood vessels, outer surface of long - Perforating fiber (Sharpey’s fibers)- anchors periosteum firmly to underlying penetrating deep into the bone matrix - Diaphysis- shaft of a long bone - Epiphyses- each end of bone a. Epiphyses are covered with a thin layer of hyaline cartilage (articular cartilage) between bones  - Marrow cavity- within diaphysis is a hollow cavity a. Contains either red or yellow bone marrow, depending on the bone and age of the individual - Compact bone – a hard, dense outer region that allows the bone to resist linear compression and twisting forces among other stresses - Spongy bone (cancellous bone)- found inside cortical bone; honeycomb-like framework of bone struts a. Allows long bones to resist force from many directions and provides a cavity for bone marrow - Endosteum- covers all inner surface of bones and bony struts of spongy bone - Epiphyseal lines- found separating both proximal and distal epiphyses from the diaphysis - Epiphyseal plates (growth plates)- a line of hyaline cartilage found in developing ones of children Short, flat, irregular, and sesamoid - These bones do not have diaphysis, epiphyses, medullary cavities, epiphyseal lines, or epiphyseal plates - Covered by periosteum with associated perforating fibers, blood vessels, and nerves like long bones - The internal structure is composed of two outer layers of thin, compact bone with a middle layer of spongy bone called diploe and its associated bone marrow - Some flat and irregular bones of the skull contain hollow, air-filled spaces called sinuses, which reduce bone weight. - Blood and nerve supply to bone: The remaining two-thirds is supplied by one or two nutrient arteries; they enter bone through a small hole in diaphysis called nutrient foramen - Nutrient arteries bypass compact bone to supply internal structures of bone - Epiphyses receive some blood supply from nutrient arteries; the majority comes from small blood vessels that enter and exit through small holes in their compact bone 4. Explain the diPerences between red and yellow bone marrow. - Red bone marrow: hematopoietic cells - Red marrow decreases a person’s age - Red marrow in adults is found only in the pelvis - Children need more red marrow growth and development  - Yellow bone marrow is composed of triglycerides, blood vessels, and adipocytes 5. Describe the inorganic and organic components of the extracellular matrix of bone tissue 1. Inorganic matrix consists of minerals that make up about 65% of bones total weight a. Made predominantly of calcium salts, bone stores about 85% of total calcium ions in the body, as well as a large amount of phosphorus b. Calcium and phosphorus salts exist as large molecules of a mineral called hydroxyapatite crystals c. Crystalline structure makes bone one of the hardest substances in the body; it makes it strong and resistant to compression d. Allows bone to be both protective and supportive e. Bicarbonate, potassium, magnesium, and sodium are also found in inorganic matrix 2. Organic matrix makes up the remaining 35% and consists of collagen fibers and ECM components a. Known as osteoid, it consists of protein fibers, proteoglycans, glycosaminoglycans, glycoproteins, and bone-specific proteins b. Collagen: predominant protein fiber; forms crosslinks with one another; helps bone resist torsion (twisting) and tensile (pulling or stretching) forces c. Collagen fibers also align themselves with hydroxyapatite crystals, enhancing the hardness of bone d. Glycosaminoglycans and proteoglycans create an osmotic gradient that draws water into osteoid; helps tissue resist compression e. Glycoproteins in osteoid bind all the diPerent components of osteoid and inorganic matric together 6. Explain the functions of the three main cell types in bone tissue. Osteoblasts: metabolically active bone cells found in the periosteum and endosteum - are bone-building cells that perform bone deposition - Bone deposition: a process where osteoblasts secrete organic matrix materials and assist in the formation of inorganic matrix Osteocytes: relatively inactive bone cells - Osteoblasts eventually surround themselves with bone matrix in a small cavity known as a lacuna; they become osteocytes that are no longer actively synthesizing bone matrix  - Appear to have the ability to recruit osteoblasts to build or reinforce bone under tension Osteoclasts: responsible for bone resorption - Cells secrete hydrogen ions and enzymes that break down bone matrix - Large multinucleated cells: resemble jellyfish; derived from a fusion of cells from bone marrow - Eventually located in a shallow depression on internal and external surfaces of bone - Hydrogen ions dissolve components of inorganic matrix - Enzymes break down organic matrix 7. Define ossification or osteogenesis. Briefly explain the diPerence between intramembranous ossification and endochondral ossification. Include examples of which bones develop from each method. - Ossification (osteogenesis): the process of bone formation - Begins in the embryonic period and continues through childhood, with most bones completing the process by age 7 - Intramembranous ossification: forms flat bones like bones of the skull and clavicles during fetal development - Endochondral ossification is bone development for all bones below the head except the clavicle; begins in the fetal stage of development for most bones o Wrist and ankles ossify much later o Occurs within a model of hyaline cartilage serves as a scaPold for developing bone 8. Describe how long bones grow in length. - Long bones grow in length called longitudinal growth - Involves division of chondrocytes (not osteocytes or osteoblast) - Takes place at the epiphysis on the side closest to the diaphysis 9. Compare longitudinal and appositional bone growth. - Longitudinal bone growth is the process in which long bones grow in length arms and legs - Appositional growth is the process of bones growing in width 10. Describe the process of bone resorption and bone deposition. 1. Bone deposition: the process in which a new bone is formed - Carried out by osteoblasts 2. Bone resorption: the process by which the old bone is removed - Carried out by osteoclasts 11. Describe the physical, hormonal, and dietary factors that influence bone remodeling. Hormones- Testosterone promotes bone deposition, estrogen inhibits osteoclast activity Age- as individuals age growth hormones and sex hormones decline Calcium ion intake-adequate to support bone deposition Vitamin D Promotes calcium ion absorption from the gut and prevents calcium ion loss in the urine Vitamin C intake-synthesis of collagen Vitamin K intake- from the diet must be adequate for the synthesis of calcium ion- binding glycoproteins secreted by osteoblasts Protein intake-collagen fibers found in an organic matrix 12. Explain the role of calcitonin, parathyroid hormone, and vitamin D in bone remodeling and calcium ion homeostasis. Calcitonin- is secreted by the thyroid gland, bone deposition; calcitonin is most active during bone growth and less so in adulthood Parathyroid hormone stimulates (PTH) -increases blood calcium ion levels Vitamin D-absorption of calcium ions from the gut